Tracking control method for reading/writing optical disk

Abstract

In a tracking control method for use in an optical disk drive to read/write an optical disk, an open-loop tracking control operation of the optical disk drive is first performed according to an input tracking error signal and a predetermined periodical offset to generate a dynamic offset. Afterwards, a closed-loop tracking control operation of the optical disk drive is performed according to the input tracking error signal calibrated with the dynamic offset.

1. A tracking control method for use in an optical disk drive to read/write an optical disk, comprising steps of:
 measuring a static offset according to an input tracking error signal generated by a detector receiving a single spot reflected from the optical disk; 
 subtracting the static offset from the input tracking error signal to be a tracking error signal without the static offset; 
 implementing a tracking servo loop with a frequency compensator-loop; 
 feeding the tracking error signal without static offset into the tracking servo loop; 
 using a first memory to learn a periodical offset in the tracking servo loop; 
 opening the tracking servo loop and driving an actuator by the periodical offset; 
 using a second memory to learn a dynamical offset according to the periodical offset; 
 subtracting the static offset and the dynamical offset from the input tracking error signal to be a tracking error signal without the static and dynamical offset; and 
 closing the tracking servo loop and feeding the tracking error signal without the static and dynamical offset into the closed tracking servo loop. 
 
     
     
       2. The method according to  claim 1  wherein the static offset is obtained by processing the input tracking error signal with a peak detector. 
     
     
       3. The method according to  claim 1  wherein the static offset is obtained by processing the input tracking error signal with a low-pass filter. 
     
     
       4. The method according to  claim 1  wherein the periodical offset indicates low frequency periodical disturbances inherent in the optical disk. 
     
     
       5. The method according to  claim 1  wherein the frequency compensator-loop comprises a filter and a gain element. 
     
     
       6. The method according to  claim 1  wherein the dynamical offset is measured as a function of the optical disk's azimuth.